Purpose:
The purpose of this work is to determine if intravitreally injected cell conditioned media (CCM) from adipose-derived stem cells (ASCs) can protect against vascular dysfunction secondary to diabetic retinopathy (DR). Previous work has demonstrated that ASCs injected intravitreally can differentiate into functional pericytes and exert a vascular protective effect, even without ASC integration into the network. The objective of this study was to isolate the contribution of a paracrine effect of ASCs in an in vivo model of retinal vasculopathy through injection of CCM.

Methods:
The stromal vascular fraction was collected from mouse gonadal adipose tissue, and ASCs were isolated through serial passage. Cells were passaged to P4 and the media was conditioned for 24 hours. CCM was concentrated to obtain soluble growth factor levels comparable to ASC populations injected in prior studies. Injections were performed once a week for four weeks in five-week-old Akimba mice to determine the impact of CCM on vascular retention in a model of DR onset. One week after the last injection, retinal wholemounts were harvested and prepared, and vascular networks were stained with lectin for analysis in ImageJ.

Results:
When injected intravitreally, CCM from healthy ASCs protect early diabetic retinal capillaries. CCM enhanced vascular stability as compared to PBS control injections. Retinal networks exhibited a reduction in capillary network dropout in the CCM injected eye. While avascular area only decreased slightly in the control injection (98.6% vs. 92.5%), vascular length density was significantly decreased. No untoward effects were noted on the neural retina or lens as a result of injection of CCM as compared to PBS control.

Conclusions:
Our data suggests ASC-derived pericytes have a paracrine effect that promotes stabilization in the diabetic retinal microvasculature. When CCM was injected intravitreally, vascular protective effects were similar to those previously observed in cell-injected studies from the same cell populations. As the vascular progenitors in adipose tissue are being evaluated for regenerative DR therapy, a CCM therapy could allow for lower-risk intravitreal injections than with potentially immunogenic ASCs. This also opens the door to future studies comparing the quality of CCM from both diabetic and healthy adipose to determine if non-autologous approaches have therapeutic potential.